With a view to meeting the requirements of surgeons, a number of supports, some floor mounted some ceiling mounted, have been proposed. Whilst the use of microscopes and related optical instruments has enabled surgeons to achieve impressive results, existing supports still have some drawbacks. It will be understood that the very restricted field of view when using a microscope at high magnification necessitates its frequent movement as an operation progresses. In some cases, using existing equipment, these movements are relatively difficult to achieve and the time in making the necessary adjustments may account for as much as 40 percent of the operating time. This is not only tiring for the surgeon but greatly increases the chance of complications for the patient. Therefore a need exists for a support whereby manipulating the microscope (or other optical instrument) requires very little effort on the part of the surgeon, but which is capable of sustaining the instrument in the required position without the surgeon having to remove his hands from the operating area to effect unclamping, adjustment, and reclamping of the apparatus.
While a number of known supports employ a combination of pivotal movements and linear (e.g. sliding) movements of components parts to provide for the desired spatial envelope of displacements of an optical instrument, it has been observed that, for the smoothest operation, a system employing only pivotal movements of component parts of the support is preferred. One such support is disclosed in UK Patent Specification No. 1357261. In the support disclosed in that specification a carrier for an optical observation device such as a binocular microscope is fixed onto an end member of a linkage rotatably mounted on a socket by means of a column, the said end member being spatially freely movable as a result of the combination of rotary movements possible about at least three axes. Furthermore, in the support disclosed in said specification, the orientation of the optical axis of the observation device may be adjusted by means of a triple axis fully universal linkage which enables freely combinable rotation thereof in three mutually perpendicular and intersecting directions by a handgrip, this linkage being effective to fix the carrier on the end member of the linkage referred to in the previous sentence. In the support disclosed in said specification a number of blocking devices are provided for clamping the carrier for the optical observation device in its desired spatial position and/or orientation, there being three of these blocking devices associated with bearings of the triple axis fully universal linkage and three more associated with bearings of the linkage rotatably mounted on said socket. The blocking devices are of the electromagnetic type, being rendered operative by the passage of electric current through coils of the blocking devices. When the surgeon wishes to adjust the position and/or orientation of the optical instrument supported on the support disclosed in said specification he actuates a switch mounted on a handgrip associated with the carrier for the instrument to effect either a complete de-energisation of the electromagnetic coils of the blocking devices or an intermittent de-energisation thereof. Counterbalancing means, comprising a weight adjustably mounted on an extension of one of the links of the linkage rotatably mounted on said socket, is provided to counterbalance gravity-produced turning moments of the entire stand in respect of the rotation axis of a parallelogram linkage to a column which is rotatable about said socket. Furthermore, by adjustment of the optical instrument on its carrier, compensation of gravity-produced turning moments of the triple axis fully universal linkage and of the optical instrument about the common intersection point of the three rotation axes is possible. These counterbalancing facilities seek to avoid unwanted movements of the optical instrument when the blocking devices are released.
While a support as disclosed in said specification goes some way to meeting the requirements of surgeons employing optical instruments such as a binocular microscope to assist them during delicate operations we have found it possible to effect further improvements in a number of respects.
The triple axis fully universal linkage of the support disclosed in said specification is a complex arrangement requiring many parts and a total of three blocking devices associated one with each of the pivots providing for rotation about said three axes. It occupies a considerable amount of space in the vicinity of the observation point and counterbalancing adjustments necessitate adjustment of the position of the optical instrument itself on its carrier. Furthermore, in the event of failure of the electrical supply, the blocking devices are unclamped permitting undesired free movement of the optical instrument.
Various objects of the invention are to overcome, or minimise, these disadvantages and provide an improved support which is compact, relatively inexpensive to manufacture, easy to adjust, and incorporate a high degree of safety in use.